Other Functions 261 



saliva (Liddell, 1936). In cats, spitting is one of the bodily expres- 

 sions of rage, probably elicited via sympathetic nerves; the llama 

 is said to use saliva for the same purpose. A function of saliva 

 specific to humans although perhaps not foreseen by nature is to 

 aid in the fixation of dentures ; the sticky saliva produced by the 

 palatine glands is supposed to be particularly valuable in this 

 respect (Ostlund, 1953). Dryness of the mouth as a side effect to 

 treatment with ganglionic blocking or parasympatholytic agents in 

 elderly persons with dentures and suffering from hypertension 

 or gastric hypersecretion may therefore be particularly incon- 

 venient. It would be fortunate if the palatine glands were endowed 

 with the ability to secrete spontaneously as assumed by Ostlund 



(!953)- 



Specific functions have been attributed to various substances 

 found in saliva. When the vasodilator effect of saliva was discovered 

 it was suggested that saliva might promote digestion in the stomach 

 and intestine by causing hyperaemia there. It was even suggested 

 that the active agent might be absorbed and play a role in the 

 regulation of the blood pressure. The agent responsible for the 

 vasodilatation was identified as kallikrein (Ungar and Parrot, 1936) 

 and found to be an enzyme acting on proteins to form a vasodilator 

 polypeptide ; the idea was put forward that this enzyme might act 

 on proteins in the food producing gastrin-releasing material and 

 thus promoting gastric digestion (Hilton and Lewis, 1955). Guim- 

 arais and Tavares (1942) found saliva to cause gastric secretion in 

 dogs and assumed this effect to be caused by the hypotensive agent 

 of saliva. Saliva has also been supposed to contain substances which 

 promote the coagulation of blood (see, e.g., Glazko and Greenberg, 

 1939; Nour-Eldin and Wilkinson, 1957). Albrechtsen and Thaysen 

 (1955), on the other hand, found a fibrinolytic activity of human 

 saliva, similar to that of milk, tears and urine; they suggested that 

 the fibrinolytic system of saliva aids in the resolution of fibrin clots 

 which might otherwise obstruct the narrow salivary ducts. Among 

 other interesting agents present in saliva, the blood group sub- 

 stances and enzymes destroying these substances may be mentioned 

 (see Kabat, 1956); it is unknown whether these substances have 

 any specific function in saliva. 



So far, the role of saliva has been mainly discussed. The salivary 

 glands may have functions other than to produce a fluid with the 

 effects dealt with above. They are usually described as having an 



